1. Field of the Invention
The present disclosure relates to a driver device to drive multiple light emission elements, a print head including the driver device, and an image formation apparatus.
2. Description of Related Art
Some conventional image formation apparatuses using electrophotography include an exposure portion formed by arranging multiple light emission thyristors as light emission elements. In such conventional image formation apparatuses that employ light emission thyristors, (of a number N where N>1), the light emission thyristors are provided per driver circuit. In addition, the position of a light emission thyristor to be illuminated is designated by using the gate of the light emission thyristor, and the illuminating power is controlled by a value of the current flowing between the anode and the cathode.
Print heads having a configuration termed as a self-scan type are already known as print heads using light emission thyristors. If a conventional self-scan type print head needs to be driven with a source voltage of, for example, 3.3 V, the source voltage of 3.3 V is not high enough to generate a gate-trigger current. An already-known technique to compensate for the shortfall is to generate a gate-trigger current by adding up the 3.3-volt source voltage and an undershoot voltage caused in the waveform of the transfer clock signal (hereinafter, “clock signal” is referred to as a “clock”).
For example, a technique disclosed in Japanese Patent Application Publication No. 2004-195796 generates a transfer-clock waveform by a clock driver circuit including two output terminals, i.e., first and second output terminals, as follows. The clock driver circuit transmits a transfer clock via the first output terminal to a CR differential circuit to generate an undershoot waveform, while transmitting the DC component via the second output terminal. Note that the reason why the two output terminals are provided for each transfer clock in the clock-driver circuit is that the CR differential circuit is incapable of transmitting the DC component.